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Base64 text & file

The text-and-file gap beside the numeric base converter and the image tool: encode text to Base64 and back with multi-byte characters intact — conversion always runs through UTF-8 bytes, never btoa on raw code units, the classic mojibake mistake the help copy explains. Toggle the URL-safe alphabet (-_ for +/) and padding; decoding tolerates whitespace and line breaks, accepts both alphabets, and names the offending character and position when the input is not Base64. A small local file (up to 10 MB) encodes to a Base64 string or a data: URI, and a Base64 string decodes to a downloadable file — with the caution that the declared content type is not verified against the bytes.

Privacy ledger

Data acquired None.
Libraries used Lit 3 — bundled into the tool file itself.
Data stored None. Files are read in memory only and never uploaded or stored.
Data transmitted None.

Use it on your own page

Download the tool as a single self-contained HTML file: readable source with the Lit library included, zero network requests — it works opened straight from your disk, and you can customize everything.

Prefer the hosted widget? One script tag embeds it and stays up to date:

<script type="module" src="https://uuutil.com/tools/base64-text.js"></script>
<uu-base64-text lang="en"></uu-base64-text>

Source license: MIT — free to use, modify and redistribute; keep the license notice in copies.